Host response in bovine mastitis experimentally induced with Staphylococcus chromogenes

Area of Science:

• Veterinary Microbiology
• Animal Immunology
• Dairy Science

Background:

• Coagulase-negative staphylococcal (CNS) intramammary infections are prevalent in dairy herds and can persist.
• Understanding the pathophysiology of CNS mastitis is crucial for effective management.
• An experimental model is needed to study host responses to CNS intramammary infections.

Purpose of the Study:

• To develop and validate an experimental model for studying host response to Staphylococcus chromogenes intramammary infection in cows.
• To characterize the clinical and subclinical manifestations of S. chromogenes intramammary infection.
• To evaluate inflammatory markers and acute-phase protein responses.

Main Methods:

• Six Holstein-Friesian cows were experimentally infected with S. chromogenes in one udder quarter.
• Clinical signs, milk production, somatic cell count (SCC), N-acetyl-beta-D-glucosaminidase (NAGase), serum amyloid A (SAA), and milk amyloid A (MAA) were monitored.
• Bacterial elimination and persistence were assessed.

Main Results:

• All cows developed infection with mild clinical signs and a 16.3% average decrease in milk production.
• Most cows eliminated bacteria within days; one developed persistent mastitis.
• SCC and NAGase returned to normal within a week, indicating mild tissue damage.
• SAA and MAA levels were elevated post-challenge, with MAA influenced by milking times.
• Systemic acute phase response (SAA) exhibited an on-off pattern.

Conclusions:

• The developed experimental model successfully mimics mild S. chromogenes intramammary infection.
• This model is suitable for investigating host responses in CNS mastitis and comparing mild versus severe infection models.
• The model provides insights into the pathophysiology and host-pathogen interactions in bovine mastitis.